1. Field of the Invention
The present invention relates to a locating structure for an optical scanning device, and more particularly to a locating structure for locating a transparency illumination module on an object focal plane of a scanner frame of a dual-mode optical scanning device.
2. Description of the Prior Art
Recently, optical scanning devices have been widely used by various users in various fields. There are many different types of scanners on market, such as hand-held scanner, scanner, transparency type scanner, and reflective type scanner. In order to meet requirements in practical use, a dual-mode optical scanning device combining reflective and transparency scanning modes has been developed.
FIG. 1 shows an exploded view of a conventional dual-mode optical scanning device comprising a reflective type scanner frame 1 and a transparency illumination module 2. The transparency illumination module 2 and the reflective type scanner frame 1 are combined in such a manner that the rear edges thereof are pivotally detachably connected by a pair of known pivot members 3. Each pivot member 3 includes a mounting rod 31 projecting from a bottom plate of the pivot member 3. A pair of shaft hole 11 are formed on the scanner frame 1 corresponding to the mounting rods 31. The mounting rod 31 is snugly fitted into the shaft hole 11, whereby the transparency illumination module 2 can be turned open about the pivot members 3 with respect to the scanner frame 1 and detachable from the scanner frame 1.
The scanner frame 1 includes a lighting source device, a traveling mechanism, and a transmission mechanism therein for scanning a reflective original document placed on the document positioning plane or object focal plane which is a top plane surface made of for example glass or other light transmittable, substantially rigid material, for supporting a document to be scanned (not shown), defining a document scanning widow.
The transparency illumination module 2 includes a back lighting source device, a traveling mechanism, and a transmission mechanism therein for scanning a transparent original document placed on the top plane surface of the scanner frame 1. A focusing lens and an image sensing device (such as Charge Coupling Element CCD) are arranged in the scanner frame 1 for receiving the scanning light beam emitted from the back lighting source device of the transparency illumination module 2 or the lighting source device arranged in the reflective type scanner frame 1.
In reflective scanning mode, a reflective original document (not shown) is placed with the surface containing the original to be scanned facing down on a transparent surface or an object focal plane of the scanner frame 1. A simple flipcover (not show) is used in reflective scanning mode to hold the reflective original document flat on the transparent surface.
The transparent surface on the scanner frame 1 is illuminated from below by lamps, producing a scan line having a scan line axis, wherein the lamps are disposed substantially parallel to the scan line axis. The scanning optics and sensor electronics are located in scan module, which is driven together with lamps such as to move the scan line from one end of the original document to the other end of the original document.
In transparency scanning mode, the flipcover used in reflective scanning mode is replaced by the transparency illumination module 2. An illumination system, shown in the drawing as lamp 126, is disposed so as to illuminate scan line 113 of the transparent original document 124 from above along scan line axis, thereby allowing scanning of the illuminated transparent original document 124 by the scan module.
The pivot members 3 not only connect the transparency illumination module 2 and the scanner frame 1 with each other, but also locate both. With reference to FIG. 2, in case that the transparency illumination module 2 is accurately located on the scanner frame 1, the scan line emitted from the back lighting source device 41 in the transparency illumination module 2 will substantially project to the image sensing device 43 through the focusing lens 42 arranged in the scanner frame 1 without deflection angle.
However, according to the conventional connection structure as shown in FIG. 1, when the transparency illumination module 2 is closed onto the scanner frame 1, the back lighting source device 41 of the transparency illumination module 1 can hardly parallel to the focusing lens 42 and the image sensing device 43 and they often contain a deflection angle xcex8 (as shown by phantom lines). In transparency scanning mode of the scanner, this deflection angle will make a part of the scan line emitted by the back lighting source device 41 unable to through the focusing lens 42 accurately project onto the image sensing device 43. This will affect the quality of image scanning. Such situation more frequently takes place in a relatively large size document scanning operation (such as standard A3 size original document).
Thus, it is desirable to provide a locating structure which is capable of overcoming the problems described above.
It is therefore a primary object of the present invention to provide a locating structure for a dual-mode optical scanning device which can be operated in a reflective scanning mode and a transparency scanning mode.
It is a further object of the present invention to provide a locating structure for locating a transparency illumination module on a top plane of a reflective type scanner frame, so as to more accurately control the relative displacement between the transparency illumination module and the scanner frame.
To achieve the above objects, in accordance with the present invention, there is provided a locating structure comprising at least one locating post projecting from a bottom surface of the transparency illumination module and facing a top surface of the reflective type scanner frame, and at least one locating hole formed on the top plane of the scanner frame and corresponding to the locating post. The locating posts clan be replaced by curved protrusions, and the locating holes can be replaced by concave portions corresponding to the curved protrusions.
To further understand the present invention, reference is made to the following detailed description of a preferred embodiment of the present invention, as well as the attached drawings, wherein: